From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 7516C2E652 for ; Mon, 19 Feb 2024 12:32:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708345948; cv=none; b=GcwZ5i+Rb9idvbZpj+EnUvZ+UPWn9UB4XLaDUl6Vg2mLPICqXBsA4sScrjGhkpaDTlGyCC+GSDMYmny5dwPXoyAeP35JLO2s2Cc3UZUrCJOJa7WPk29BQYoxTAKEVgBTgpyAHz+FH82UitUUboi7l37u4AkOQOepKjEPlHdhdM8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708345948; c=relaxed/simple; bh=TpY5wvjvpTME5DvC+TJRlgikQDnOPMM1tS9WDjvoTMs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=CedZjR87LDKLtjhJNMSXg1e1hTwpNg+BOQRfurk+QYLzFrojiW6I4wEMxehsRYUCUELcVqYF2UM/vzHMMxxaBgAu2Hvpza55Hs+2TlooN9pB8chY+O/zHtGcFX3xQbYfGEPnyCmvjip9PJV1fq350i+IgxwRBIue2vVpDjuSyTg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8DBE6FEC; Mon, 19 Feb 2024 04:33:05 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.66.18]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EE45B3F73F; Mon, 19 Feb 2024 04:32:20 -0800 (PST) Date: Mon, 19 Feb 2024 12:32:18 +0000 From: Mark Rutland To: Ankur Arora Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, peterz@infradead.org, torvalds@linux-foundation.org, paulmck@kernel.org, akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, willy@infradead.org, mgorman@suse.de, jpoimboe@kernel.org, jgross@suse.com, andrew.cooper3@citrix.com, bristot@kernel.org, mathieu.desnoyers@efficios.com, geert@linux-m68k.org, glaubitz@physik.fu-berlin.de, anton.ivanov@cambridgegreys.com, mattst88@gmail.com, krypton@ulrich-teichert.org, rostedt@goodmis.org, David.Laight@aculab.com, richard@nod.at, mjguzik@gmail.com, jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com Subject: Re: [PATCH 17/30] x86/thread_info: define TIF_NEED_RESCHED_LAZY Message-ID: References: <20240213055554.1802415-1-ankur.a.arora@oracle.com> <20240213055554.1802415-18-ankur.a.arora@oracle.com> <874jeardni.fsf@oracle.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <874jeardni.fsf@oracle.com> On Wed, Feb 14, 2024 at 12:31:29PM -0800, Ankur Arora wrote: > Mark Rutland writes: > > On Mon, Feb 12, 2024 at 09:55:41PM -0800, Ankur Arora wrote: > >> diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h > >> index d63b02940747..88c1802185fc 100644 > >> --- a/arch/x86/include/asm/thread_info.h > >> +++ b/arch/x86/include/asm/thread_info.h > >> @@ -81,8 +81,11 @@ struct thread_info { > >> #define TIF_NOTIFY_RESUME 1 /* callback before returning to user */ > >> #define TIF_SIGPENDING 2 /* signal pending */ > >> #define TIF_NEED_RESCHED 3 /* rescheduling necessary */ > >> -#define TIF_SINGLESTEP 4 /* reenable singlestep on user return*/ > >> -#define TIF_SSBD 5 /* Speculative store bypass disable */ > >> +#ifdef CONFIG_PREEMPT_AUTO > >> +#define TIF_NEED_RESCHED_LAZY 4 /* Lazy rescheduling */ > >> +#endif > >> +#define TIF_SINGLESTEP 5 /* reenable singlestep on user return*/ > >> +#define TIF_SSBD 6 /* Speculative store bypass disable */ > > > > It's a bit awkward/ugly to conditionally define the TIF_* bits in arch code, > > and we don't do that for other bits that are only used in some configurations > > (e.g. TIF_UPROBE). That's not just for aesthetics -- for example, on arm64 we > > try to keep the TIF_WORK_MASK bits contiguous, which is difficult if a bit in > > the middle doesn't exist in some configurations. > > That's useful to know. And, I think you are right about the > ugliness of this. > > > Is it painful to organise the common code so that arch code can define > > TIF_NEED_RESCHED_LAZY regardless of whether CONFIG_PREEMPT_AUTO is selected? > > So, the original reason I did it this way was because I wanted to have > zero performance impact on !CONFIG_PREEMPT_AUTO configurations whether > TIF_NEED_RESCHED_LAZY was defined or not. > (I was doing some computation with TIF_NEED_RESCHED_LAZY at that point.) > > Eventually I changed that part of code but this stayed. > > Anyway, this should be easy enough to fix with done #ifdefry. > > Thanks for reviewing. Great! BTW, the series overall looks to be in very good shape; thanks a lot for working on this! Mark.